Health: Oxytocin Causes Mental and Physical Reactions

(be aware of the effects of oxytocin in nasal sprays)

1. A hormone produced by the hypothalamus that is stored and released by the pituitary gland. It causes contractions of the uterus and the release of milk from the mammary glands.
2. A smooth muscle contraction-stimulating hormone found in the neurohypophysis.
3. A hormone made in the brain that plays a role in childbirth and lactation by causing muscles to contract in the uterus (womb) and the mammary glands in the breast. Animal studies have shown that oxytocin also has a role in pair bonding, mate-guarding, and social memory.
4. A peptide (a compound consisting of two or more amino acids) that is secreted by the hypothalamus and transported to the posterior lobe of the pituitary gland at the base of the brain. Oxytocin is related to another hormone called vasopressin.
5. In pharmacy, a commercial form of this substance, obtained from beef and hog pituitary glands or; especially, by synthesis, and used chiefly in obstetrics to induce labor and to control postnatal hemorrhage.
6. Nasally administered oxytocin appears to generate trust in humans.

In a 2005 study, it was shown that in a risky investment game, experimental subjects given the hormone displayed what the researchers deemed "the highest level of trust" twice as often as the control group who were given placebos.

The same experiment with the subjects told that they were interacting with a computer showed no such reaction, leading to the conclusion that oxytocin was not merely affecting risk-aversion.

7. Various anti-stress functions: reducing blood pressure and cortisol levels, increasing tolerance to pain, reducing anxiety.

Oxytocin may play a role in encouraging "tend and befriend", as opposed to "fight or flight", behavior, in response to stress.

The hormone best known for its role in inducing labor may influence our ability to bond with others

In a preliminary study, the hormone oxytocin was shown to be associated with the ability to maintain healthy interpersonal relationships and healthy psychological boundaries with other people.

This is one of the first researches into the biological basis for human attachment and bonding. One study indicated that oxytocin may be mediating emotional experiences in close relationships.

General knowledge has been established of the important role oxytocin plays in the reproductive life of mammals. The hormone facilitates nest building and pup retrieval in rats, acceptance of offspring in sheep, and the formation of adult pair-bonds in prairie voles. In humans, oxytocin stimulates milk ejection during lactation, uterine contraction during birth, and is released during orgasm in both men and women.

Inhaling oxytocin can have strong influences

Men who inhale a nasal spray spiked with oxytocin give more money to partners in a risky investment game than do men who sniff a spray containing no active ingredient, say economist Ernst Fehr of the University of Zurich and his colleagues.

Previous studies of nonhuman animals had suggested that oxytocin in the brain encourages long-term mating in pairs of adults and nurturing behaviors by mothers toward their offspring. This substance, which works as both a hormone and a neurotransmitter, fosters the trust needed for friendship, love, families, economic transactions, and political networks, Fehr proposes.

"Oxytocin specifically affects an individual's willingness to accept social risks arising through interpersonal interactions," he and his colleagues conclude in the June 2, 2005, of Nature magazine.

Scientists studied oxytocin's influence on male college students playing an investment game.

The oxytocin influence is "a remarkable finding," says neuroscientist Antonio Damasio of the University of Iowa College of Medicine in Iowa City in an editorial published with the new report. Damasio had previously argued that the hormone acts somewhat as a love potion. "It adds trust to the mix, for there is no love without trust," he says.

Worries may arise that crowds of people will be sprayed with oxytocin at political rallies or other events to induce trust in speakers, Damasio notes. However, he proposes that slick marketing strategies for political and other products probably already trigger oxytocin release in many consumers.

Fehr's group plans to determine what brain networks participate in oxytocin-inspired trust decisions and to consider whether oxytocin might counter social phobia and other mental disorders that result in social avoidance.

— Excerpts from Science News Online, by Bruce Bower; June 4, 2005.

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